In this guide, you'll learn how to generate a **TypeScript SDK** for your FastAPI backend.

## Open Source SDK Generators { #open-source-sdk-generators }

A versatile option is the [OpenAPI Generator](https://openapi-generator.tech/), which supports **many programming languages** and can generate SDKs from your OpenAPI specification.

    private final OneSizeTestContainerGenerator<BiMap<K, V>, Entry<K, V>> generator;

    public MapGenerator(
        OneSizeTestContainerGenerator<BiMap<K, V>, Entry<K, V>> oneSizeTestContainerGenerator) {
      this.generator = oneSizeTestContainerGenerator;
    }

    @Override
    public SampleElements<Entry<K, V>> samples() {
      return generator.samples();
    }

    @Override

import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * To be implemented by test generators that can produce test subjects without requiring any
 * parameters.
 *
 * @param <T> the type created by this generator.
 * @author George van den Driessche
 */
@GwtCompatible
@NullMarked
public interface TestSubjectGenerator<T extends @Nullable Object> {

        // We skip it when container is not initialized
        try {
            HtmlTagBasedGenerator generator = new HtmlTagBasedGenerator();
            ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
            File outputFile = File.createTempFile("generator_", ".png");

            String imagePath = "thumbnail/600x400.png";

    private final OneSizeTestContainerGenerator<BiMap<K, V>, Entry<K, V>> generator;

    public MapGenerator(
        OneSizeTestContainerGenerator<BiMap<K, V>, Entry<K, V>> oneSizeTestContainerGenerator) {
      this.generator = oneSizeTestContainerGenerator;
    }

    @Override
    public SampleElements<Entry<K, V>> samples() {
      return generator.samples();
    }

    @Override

// needs to be added separately otherwise Gradle will quote it and javac will fail
tasks.named("compileJava").configure {
  options.compilerArgs.addAll(["-processor", "org.openjdk.jmh.generators.BenchmarkProcessor"])
}

tasks.register('copyExpression', Copy) {
  dependsOn configurations.expression
  from { configurations.expression.collect { zipTree(it) } }
  into "${buildDir}/plugins/expression"
}

import java.util.Collection;
import java.util.List;
import java.util.Map;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * To be implemented by test generators of things that can contain elements. Such things include
 * both {@link Collection} and {@link Map}; since there isn't an established collective noun that
 * encompasses both of these, 'container' is used.
 *

import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * To be implemented by test generators that can produce test subjects without requiring any
 * parameters.
 *
 * @param <T> the type created by this generator.
 * @author George van den Driessche
 */
@GwtCompatible
@NullMarked
public interface TestSubjectGenerator<T extends @Nullable Object> {

import java.util.Collection;
import java.util.List;
import java.util.Map;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * To be implemented by test generators of things that can contain elements. Such things include
 * both {@link Collection} and {@link Map}; since there isn't an established collective noun that
 * encompasses both of these, 'container' is used.
 *

                  CollectionFeature.RESTRICTS_ELEMENTS,
                  ListFeature.SUPPORTS_SET)
              .createTestSuite());
    }
    return suite;
  }

  // Test generators.  To let the GWT test suite generator access them, they need to be
  // public named classes with a public default constructor.

  public static final class DoublesAsListGenerator extends TestDoubleListGenerator {
    @Override